An 18-year-old Dixon High School student was arrested Thursday on suspicion of altering a computer data system, a felony, in connection with more than 200 grade changes for more than 30 students at the school.

Senior Juan Ambriz was taken into custody at the 555 College Way campus by Dixon police after Dixon Unified School District officials uncovered the scandal and said they gathered enough information to conclude he had breached the electronic gradebook system and made the changes.

Dixon Police Chief Jon Cox said Ambriz, who was booked into Solano County Jail, “was cooperative” at the time of his arrest and the case has been turned over the Solano County District Attorney’s Office “to determine if the matter goes forward and charges will be filed.”

He released no additional details about Ambriz or the suspected crime.

Superintendent Brian Dolan, who issued a press release Thursday, said the district’s investigation was ongoing and that he had conferred with school staff about the suspected crime, which he called “a hacking” that may involve others besides Ambriz.

Clearly dismayed during a telephone interview, Dolan also spoke with the district’s legal counsel, who is advising him about the investigation and possible consequences for students, most of them seniors, some of whom have already been accepted to colleges, including the U.S. Air Force Academy, Stanford and Ivy League universities, among others. Discipline may include disallowing some students to graduate, or possibly suspension and explusion.

“Some are in danger of not graduating,” he said, declining to be specific about Ambriz’s status.

In the coming days, district administrators, Dixon High School Principal Nick Girimonte and vice principals will continue to interview students to determine exactly “who was engaged in this fraud,” which appeared to involve grade changes to specific assignments, not a report card, said Dolan.

“How many were directly involved (possibly other than merely Ambriz)?” he wondered, adding, “It’s certainly conceivable that some students may not have been aware or they made direct requests. We’ll also explore whether or not parents may have been involved.”

Dolan said there was “clear evidence” that grades were changed across nine different teacher gradebooks “in a variety of classes,” with some changes going as far back as January.

As for the costs to the district to continue the investigation, he said, “It costs us our time.”

Girimonte, the school’s vice principal and other staffers have virtually done little else but deal with the investigation, which began Tuesday when a teacher noticed the changes, Dolan said.

He predicted the investigation would continue nonstop for several more days, as students, one by one, are questioned and interviewed, and reports are written.

“It’s time-consuming,” Dolan said of the investigation.

The scandal comes at a time when teachers are “in a frantic push” to make sure seniors complete their academic requirements and graduate, noted Dolan, adding that the high school atmosphere was, until Ambriz’s arrest, somewhat celebratory before the scheduled June 6 commencement.

“It’s a punch in the gut,” he said. “It really feels like a punch in the gut. The staff has been working hard with the students all year long. The teachers give and give and give and you kind of trust them (the students) to do the right thing … there’s a feeling of betrayal that is strong and it’s really distressing.”

Saying the recent events “have become a huge topic of conversation,” Dolan added, “We’re not hiding from it. We put the press release up on Facebook.”

In the release, Dolan said, “the student (not specifically identified) explained how the grades had come to be changed. A second student was interviewed and confirmed the same information. Both students described how another student had gained access to teachers’ online electronic gradebooks and had the capability to change the grades on any assignment in them.”

Afterward, district staffers generated reports from the student information system, documenting the number of grade changes made, the specific changes made, by student and assignment, as well the details about dates and times. District investigators were also able to obtain the Internet provider address of the computer used to make the grade changes and verify that it was not a district computer, noted Dolan.

School staffers later questioned the student, which Dolan did not identify in the release as Ambriz, and presented documents generated by the technology staff.

In the release’s wording, Dolan described Ambriz as “cooperative with staff under questioning and made a full and detailed admission of how he accessed the electronic gradebooks.”

He ended the written statement with a quotation: “I am joined by the staff at Dixon High in expressing my profound disappointment with regard to this situation. The fact that one student was both able to and did change grades is distressing. The additional fact that more than 30 other students appear to have enlisted his assistance in these dishonest and unethical acts is of grave concern to all of us.”

Dolan, in a telephone interview, added, “If we don’t address this, the students learn that it’s OK, but it’s not OK. We’re going to deal with it, follow the law and honor due process, and then make decisions about what will happen to the students. That will take time.”

The Dixon grade-changing scandal is the second one in Solano County within the past year. In November at Armijo High School in Fairfield, a teacher was placed on administrative leave and later resigned after he was suspected of changing the grades of several students in the school’s International Baccalaureate program.